Looks like a starter egg but...

So this looks like a starter egg but I have 6 hens who are well over a year old and have been giving me 4 or 5 eggs a day this year (6 on Sunday!). Plus I have 3 pullets, 2 RIR and 1 Plymouth Roc, who are about 12 weeks old. On Saturday we switched the pullets from mash to grower pellets but they have been free ranging the backyard with the hens for a few weeks now. I think it is impossible for one of the pullets to be laying so I am now worried about one of my hens. Anyone have any ideas?